1. Performance Predictions for Carbon Nanotube Field-Effect Transistors
D.L. Pulfrey, D.L. John, L.C. Castro
Department of Electrical and Computer Engineering
University of British Columbia
Vancouver, B.C. V6T1Z4, Canada

2. Single-Walled Carbon Nanotube
Hybridized carbon atom  graphene monolayer  carbon nanotube
2p orbital, 1e- (-bonds)

3. VECTOR NOTATION FOR NANOTUBES
Zig-zag (6,0)
Chiral tube
(5,2) Tube
Structure (n,m):
Armchair (3,3)
Adapted from Richard Martel

4. Compelling Properties of Carbon Nanotubes
NANOSCALE -- no photolithography
BANDGAP TUNABILITY eV
METALS AND SEMICONDUCTORS -- all-carbon ICs
BALLISTIC TRANSPORT nm
STRONG COVALENT BONDING
-- strength and stability of graphite
-- no surface states (less scattering, compatibility with many insulators)
HIGH THERMAL CONDUCTIVITY
-- almost as high as diamond (dense circuits)
SELF-ASSEMBLY -- biological, recognition-based assembly

5. Self-assembly of DNA-templated CNFETs K.Keren et al., Technion.

6. Self-assembly of DNA-templated CNFETs K.Keren et al., Technion.

7. CLOSED COAXIAL NANOTUBE FET STRUCTURE
chirality: (16,0)
radius: 0.62 nm
bandgap: 0.63 eV
length: nm
oxide thickness: (RG-RT): nm

8. MODE CONSTRICTION and TRANSMISSION E T kz CNT (few modes) kx
Doubly degenerate lowest mode T
CNT (few modes)
Interfacial G: even when transport is ballistic in CNT
METAL (many modes)
155 S for M=2

9. CURRENT in 1-D SYSTEMS
The Landauer current

10. General non-equilibrium case
1D DOS E
f(E)
EFS
0.5 E
f(E)
EFD
0.5
Non-equilib f(E-EC,z)
Q(z,E)=qf(E-EC,z)g(E-EC,z)
Solve:
1. Self-consistent SP
2. Compact model

11. Quantum-mechanical treatment
Need full QM treatment to compute:
-- Q(z) within barrier regions
-- Q in evanescent states (MIGS)
-- resonance, coherence
-- S  D tunneling.
Quantum-mechanical treatment
Emid

12. Transmission Probability TS ComparisonSP
CM2
CM1
VGS=VDS=0.4 V
Emid
D.L. John et al., Nanotech04, March 2004

13. Drain I-V Comparison CM1 VGS=0.4V CM2 SP
L.C. Castro et al., Nanotechnology, submitted.

14. I-V dependence on S,D workfunction
Negative barrier
(p-type) device
Positive barrier (p-type) device
VGS = -0.4 V
D.L. John et al., Nanotech04, March 2004

15. gate
Cins Q
insulator
Quantum Capacitance CQ
nanotube
source

16. "Quantum" Capacitance in CN
VDS=0
VDS=0.2V
Band 1
Band 2
D.L. John et al., JAP, submitted.

17. Transconductance: the Ultimate Limit
f(E)
EFS
0.5
EFD EC

18. CONCLUSIONS CNs have excellent thermal and mechanical properties.
CNFETs can be self-assembled via biological recognition.
QMR is important in negative-barrier SB-CNFETs.
High DC currents and transconductances are feasible.
Capacitance is not quantized.
CNFETs deserve serious study as molecular transistors.